Fluid pressure operable brake control valves

ABSTRACT

A triple valve for fluid operable braking is provided with an additional emergency braking valve portion which has its own pressure responsive member which is responsive to at least a predetermined reduction of brake pipe pressure relative to quick action chamber pressure in a given period of time to open a brake cylinder valve to apply pressure to the brake cylinder from a reservoir and open a vent valve to vent the brake pipe, the vent valve and the brake cylinder valve being arranged in line and having between them an accelerated release valve which on return movement of the pressure responsive member past its initial position, is allowed to open to connect brake cylinder to brake pipe until the latter are within a predetermined pressure of each other.

Paginton FLUID PRESSURE OPERABLE BRAKE CONTROL VALVES [75] Inventor:Philip Norman Paginton, London,

England [73] Assignee: Westinghouse Brake and Signal Company, Limited,London, England [22] Filed: May 28, 1971 [21] Appl. No.: 147,749

[30] Foreign Application Priority Data June 9, 1970 Great Britain..27,924/70 [52] US. Cl ..303/33, 303/37 [51] Int. Cl. ..B60t 15/22 [58]Field of Search ..303/33, 37, 39, 43, 303/69, 81

[56] References Cited UNITED STATES PATENTS 1,895,464 l/l933 Hewitt..303/37 X F162. FIG. I.

SERVICE PORTION 3,472,562 10/1969 Washboum ..303/33 X PrimaryExaminer-Duane A. Reger Attorney-Larson, Taylor & Hinds A triple valvefor fluid operable braking is provided with an additional emergencybraking valve portion which has its own pressure responsive member whichis responsive to at least a predetermined reduction of brake pipepressure relative to quick action chamber pressure in a given period oftime to open a brake cylinder valve to apply pressure to the brakecylinder from a reservoir and open a vent valve to vent the brake pipe,the vent valve and the brake cylinder valve being arranged in line andhaving between them an accelerated release valve which on returnmovement of the pressure responsive member past its initial position, isallowed to open to connect brake cylinder to brake pipe until the latterare within a predetermined pressure of each other.

ABSTRACT 5 Claims, 2 Drawing Figures PATENTEDMAY 81975 3,731,982 sum 1"or 2 l9 8 SERVlCE PORTION FIG. I.

FLUID PRESSURE OPERABLE BRAKE CONTROL VALVES This invention relates tofluid pressure operable brake control valve apparatus and relates moreespecially to an emergency braking control valve operable in response tomore than a predetermined rate and amount of change of a controllingfluid pressure to supplement a brake effort controlled by a servicevalve portion.

According to the present invention there is provided fluid operablebrake control valve apparatus for controlling, in response to brake pipepressure, the supply of fluid under pressure into and out of a brakecylinder, the apparatus including a pressure responsive membermechanically linked to a vent valve and a brake cylinder valve andmovable in one direction from a predetermined position in response to apredetermined change of brake pipe pressure in relation to a referencepressure in a given time to on the one hand open the vent valve to ventthe brake pipe and thus enhance the change of pressure and on the otherhand to open the brake cylinder valve to effect communication betweenthe fluid pressure reservoir and the brake cylinder, the pressureresponsive member subsequently being displacable in the other directionto permit reclosure of the said valves and owing to a drop in thereference pressure being responsive to a recovery of brake pipe pressurerelative to the reference pressure to permit opening of an acceleratedrelease valve to connect said brake cylinder to said brake pipe.

The vent valve, brake cylinder valve and accelerated release valve maybe disposed in line.

The accelerated release valve may be a valve so spring loaded as tofunction as a check valve to close when the brake pipe pressure hasrecovered to within a predetermined amount of brake cylinder pressure.

The apparatus may be operable as an emergency braking control valveportion in conjunction with a service braking control valve portionoperable to control the application of fluid pressure from an auxiliaryreservoir to the brake cylinder in dependence upon the differencebetween brake pipe and auxiliary reservoir pressures and the saidaccelerated release valve of the emergency portion may be operable whenopen to also connect the auxiliary reservoir to the brake pipe.

In the embodiment of the invention about to be described, it may beobserved that the vent valve via which the brake pipe is ventable toatmosphere, the high pressure valve via which the emergency reservoir isconnectable to the brake cylinder and the accelerated release valve areall arranged in line and this ensures a desired sequence of operationboth during emergency application, and during release.

In order that the invention may be more clearly understood and readilycarried into effect, the same will be further described by way ofexample with reference to FIGS. 1 and 2 of the accompanying drawingswhich together illustrate a control valve comprising an emergencyportion, a manifold portion and a service portion and the manner inwhich these portions are interconnected to constitute one embodiment ofthe invention as for operation.

Referring to the drawings, the service portion, the manifold portion,and the emergency portion are correspondingly labelled and the manifoldportion is provided with ports for connection to the brake pipe (13?),brake cylinder (BC), emergency reservoir (ER), brake cylinder exhaust(EX) and auxiliary reservoir (AR). The brake cylinder, emergency andauxiliary reservoirs are not shown but are assumed to be appropriatelyconnected and as will be seen hereafter, the latter reservoirs arechargeable in the charging mode from the brake pipe (BP). The manifoldportion also includes in addition to the various airways to be referredto in greater detail hereafter, an air filter (AF) via which allincoming brake pipe air has to pass before communicating with either ofthe pressure responsive members in the emergency portion or the serviceportion of the apparatus. The manifold portion also includes a quickaction chamber (QAC) further reference to which will be made hereafter.

Referring now to the service portion, this bears considerable similarityto the brake control apparatus which is described .in some detail in theSpecifications of co-pending patent applications Ser. Nos. 115,650 and115,651. Certain detail differences will however become apparent. Forexample, the accelerated release reservoir of the above-numberedApplications if provided by the emergency reservoir of the presentembodiment. Further, associated with the auxiliary reservoir chargingvalve of the present arrangement, there is a further valve which isoperated from the same stern for charging the emergency reservoir. Also,retarded recharge valve means is provided associated with the auxiliaryreservoir charging stroke and a service portion inshot valve is providedwhich is operable to provide an inshot of air to the brake cylinder fromthe auxiliary reservoir upto a predetermined pressure of say 12 p.s.i.An emergency portion inshot valve is also similarly provided.

The service portion of the apparatus consists essentially of a mainpressure responsive member 1 slidably carried on a stem 2 in the housingof the service portion and the pressure responsive member 1 along withits flexible diaphragm 3 constitutes a partition between a chamber (b)which is connected to brake pipe and a chamber (a) which is connected toauxiliary reservoir. The pressure responsive member 11 carries a brakecylinder inlet valve represented by reference 4 and a brake cylinderexhaust valve represented by reference 5 each being operated by theupward or downward movement respectively of the pressure responsivemember. Also coupled to the member 1 is the auxiliary reservoir chargingvalve 6 and associated therewith an emergency reservoir charging valve7. Finally, the central stem 2 which is sealingly slidable in thehousing is coupled via a rod 8 to a quick service and inlet exhaustvalve assembly represented generally by the reference 9. The quickservice inlet and exhaust valves have a composite closure member 10which is seatable on the one hand against a lower piston operatedslidable member 11 andan upper slidable sleeve member 12. The quickservice inlet and exhaust valve structure is the subject inter alia ofthe first of the aforementioned copending patent applications.

As described previously in this last mentioned copending Application,the arrangement is provided with a quick service bulb capacity 14 whichis connected on the one hand to the underside of the stem 2, and on theother hand to the underside of the slidable member 11 which normallyrests in the position shown against a housed spring 15.

The brake cylinder exhaust valve has its exhaust side connected via achoke 16 to one side of a pressure responsive member 17 on the otherside of which is connected via an unimpeded passage R1 to the exhaustside of the valve 5. The pressure responsive member 17 operates a ballvalve 18 on exhausting of the brake cylinder to enable an acceleratedrelease to occur by virtue of a transient transfer of fluid pressurefrom the emergency reservoir to the brake pipe thereby assisting therelease. This is described in more detail in the second of theabove-mentioned co-pending patent applications, and the interconnectionswhich are provided inter alia via the further check valve 19 forachieving such operation will not be specifically pointed out furtherherein. The brake cylinder service inshot valve is shown in the drawingsas valve 20 and this is controlled by brake cylinder pressure by meansof a pressure responsive member 21 which is spring loaded by a spring 22to hold the valve 20 in an open position up to brake cylinder pressuresof about 12 p.s.i. In the closed position of the valve 20 above suchpressures, the passage between the auxiliary reservoir via the valve 4and the brake cylinder is restricted to that through a choke 23. Alsocoupled to the body of the inshot valve 23 and actuable by the pressureresponsive member 21 there is a brake cylinder maintaining valve 24 viawhich and choke 26, the brake cylinder is connectable to the quickservice bulb capacity 14.

The retarded recharge valve to which reference has already been made, isrepresented by the valve and this again is operable via a rod by apressure responsive member 31 and the underside of which is subject, inthe position of the service portion shown, to auxiliary reservoirpressure via the auxiliary reservoir charging valve 6. The pressureresponsive member 31 is spring loaded on the underside and the upperside is connected to the auxiliary reservoir via the valve 6 through achoke 33. The path to the retarded recharge valve 30 from brake pipe isvia a check valve 34 or a choke 35 which is parallel with this checkvalve.

The emergency portion of the apparatus consists of a pressure responsivemember denoted generally by the reference which with a diaphragm 41provides separation between upper and lower chambers (q) and (p),respectively the upper chamber (q) being connected to the quick actionchamber (QAC) referred to previously and the lower chamber (p) isconnected via the air filter AF to the brake pipe BP. The pressureresponsive member 40 is mounted on a sealingly slidable rod 43 via whichon a downward movement it can cause opening of a vent valve member 44connected between the brake pipe via a coarse filter 45 and atmosphere.The valve 44 is normally biassed into the closed position by a spring 46and the valve member 44 is also sealingly slidable on an extension ofthe rod 43 which further engages an emergency accelerated release valvemember 47 which is also itself subject to a spring pressure effected bya spring 48 between members 44 and 47. The valve member 47 seats againsta slidable valve seat 49 via which when separated from 47 there is apassage between the brake cylinder and the brake pipe. The lower end ofthe slidable valve seat member 49 is engagable with a high pressurevalve closure member 50 which is spring biassed by a spring 51 into theclosed position in which it seals a path between the emergency reservoirand the brake cylinder.

A check valve 52 is provided between the quick action chamber and theemergency reservoir as indicated and also associated with the emergencyportion there is as mentioned previously an emergency inshot valve whichcomprises a valve closure member 53 which is maintained in an opencondition by the pressure of a spring 54 against a pressure responsivemember 55 the member 55 only being displaceable against the spring whenthe brake cylinder pressure has attained a value of approximately 12psi. At this value, the valve closure member 53 is closable to restrictthe path to the brake cylinder to that which is provided via a choke 56.

In order to secure the desired operation within the emergency portion ofthe apparatus, there are provided between the chambers (q) and (p),conveniently in the pressure responsive member itself, arrangements ofsuitably spring loaded check valves and choke means. In the presentembodiment, there are three check valves 57, 58 and 59. The valve 58 isthe choke varying valve and being centrally located, is liftable off itsseat in the position of the member 40 as shown, by a centrally disposedneedle 60 located with the housing, to provide a by-pass of a choke 62via the check valve 57. Again, each of the check valves 57 and 59 has arespective associated choke 63 and 64. As will be seen hereafter, thecheck valve 59 operates as a quick action chamber charging check valveand the check valve 57 serves as an overcharge dissipation check valvefor the quick action chamber (QAC).

Referring now to the operation of the apparatus, it will be understoodat the outset, that the apparatus is required to control in response toapplied brake pipe pressure, the braking pressure applied from auxiliaryand/or emergency reservoirs, to a brake cylinder. The apparatus in thepresent instance is so designed as to control in response to a reductionof brake pipe pressure, an increase of braking pressure to the brakecylinder and vice versa. RElease of the brakes is therefore achievableby a return of brake pipe pressures to a normal operating brake pipepressure. Furthermore, the apparatus is specifically designed for use ina vehicle which forms part of a train of further vehicles each havingidentical sets of braking apparatus connected to a common brake pipe.

Considering therefore the charging operation effected from the brakepipe when the brake pipe is pressurized from a drivers brake controlvalve, air from the brake pipe enters the apparatus at the port BP,passing via the air way B2 through the air filter AF, passages B3 and B4to the chamber (b above the pressure responsive member I of the serviceportion. Brake pipe pressure also flows from the passage B3 via passageB5 into passage B7 and through the sensitivity check valve 34 to theretarded recharge valve 30 the position of which at this time is asshown due to the pressure of the spring 32. There is therefore a flow ofair via the valve 30 and the auxiliary reservoir charging choke 33 andthe air way A2 to the auxiliary reservoir charging valve 6 which is alsoin the open position and provides a passage via A1 to the auxiliaryreservoir. The pressure in the auxiliary reservoir is also communicatedvia the air way A3 to the lower side (a) of the pressure responsivemember 1 of the service portion of the apparatus. By virtue moreover ofthe fact that auxiliary reservoir pressure is also applied from thepassage A2 to the lower side of the pressure responsive member 31 whichcontrols the retarded recharge valve 30, dependent upon the value of thespring 32, the valve 30 can maintain a substantially constantdifferential across the charging choke 33. This assists uniform chargingthroughout a train of vehicles connected to a common brake pipe.

Brake pipe air is also applied from the passage B5 referred to above tothe passage B6 which is connected to the underside of the quick servicevalve lltl of the service portion and a passage for brake pipe air isalso provided via the coarse filter 45 and the air way B1 to the regionbeneath the vent valve 44 referred to above. Additionally, air from thebrake pipe via the filter AF can flow via the passage B8 to the chamber(p) beneath the pressure responsive member 40. Air from the chamber (p)then flows via the charging choke 64 and the quick action chambercharging check valve 59 to the quick action chamber via the air way (qCharging of the emergency reservoir which is connected at the point ERof the manifold portion of the apparatus is effected from the auxiliaryreservoir via the passage Al leading to the valve 6, the charging checkvalve 7, and the airway E4 into the airway E3 connected to the emergencyreservoir. It will be appreciated therefore that emergency reservoirpressure is applied via the check valve 19 to the upper side of theaccelerated release valve 18 and the emergency reservoir thereforeconstitutes a source of accelerated release air for the operation of theaccelerated release valve.

When the system is fully pressurized and a stable condition exists, thepressure differential which is effective on the pressure responsivemember 1 of the service portion due to brake pipe pressure acting overthe area of the stem 2 against atmospheric pressure which at this timeis present in the quick service bulb 14 due to the quick service exhaustvalve being open, maintains the service portion in the position shown.In this position, the valve 5 is in the position shown and the brakecylinders are therefore vented to atmosphere and the accelerated releasevalve l8 rests in the closed position due to the slight downward thrustprovided by the pressure responsive member 17.

Ignoring for the present, the operation of the emergency portion andindeed, assuming that the brake pipe pressure is controlled at acontrolled rate such that the emergency portion does not operate, thepressure in the chamber (b) above the pressure responsive member 1 ofthe service portion is reduced and the differential causes the pressureresponsive member to rise against the stabilizing pressure of the mainstem. Such movement causes the quick service inlet valve 10 to lift fromits slidable valve seat which is held down against the housed spring bythe brake pipe pressure in the passage B6. Opening of the valve 1H)allows brake pipe air to flow into the quick service bulb capacity 14via passages B5, B6 and S1 and S2 and there is a consequential immediatedrop of pressure above the pressure responsive member 1 in the chamber(b). The presure responsive member therefore tends to move up morerapidly and the quick service bulb capacity M is sealed off fromatmosphere by engagement of the valve member M) with the slidable valveseat lit. The pressure across the quick service control piston at thelower end of the slidable member if then equalizes and this permits thelight spring loading beneath it to cause the member 11 to move upwardsto its uppermost position. in this position, the quick service inletvalve is not closed because the upward movement of the main stem hascarried with it the slidable portion 12 to a point at which the portion12 engages with its upper stop at which point he valve seat 10 isseparated from the slidable member 11. The upward movement of 12 isachieved and maintained by virtue of the bulb pressure acting on thearea of the valve plus the sleeve l2, as compared with atmosphericpressure which exists in the quick service bulb exhaust passage.

During the rapid upward movement of the pressure responsive member 1 andthe stem 2, the brake cylinder exhaust valve 5, the auxiliary reservoircharging valve 6 and the emergency reservoir charging valve 7 close,followed by the opening of the brake cylinder inlet valve 4. Auxiliaryreservoir air therefore flows via the passage A3, the chamber (a)beneath the pressure responsive member 1 and the brake cylinder inletvalve 4 to the service inshot valve 20 which is open and therefore thisair flows to the brake cylinder via the passages A5, A6, A7, A3, theemergency inshot valve 53 in the open condition, the passage C1 to thebrake cylinder BC. As mentioned previously both inshot valves 20 and 53remain in the open condition until the brake cylinder pressure hasattained a pressure of approximately l2 p.s.i. At this point the inshotvalves close and reduce the initially large opening to the brakecylinder to a passage which is controlled by the choke 23 associatedwith the service inshot valve or the choke 56 associated with theemergency inshot valve, as the case may be.

The rise of brake cylinder pressure depends upon the degree of reductionin brake pipe pressure and if the brake pipe reduction is not sufficientto produce the required pressure, the brake cylinder maintaining valve24 does not close and the connection exists between the quick servicebulb l4 and brake pipe and the brake cylinder via passages S2, S3, choke26, and the valve 24 to the brake cylinder via passage A6 and theemergency portion. Brake pipe pressure is therefore reduced by flow intothe brake cylinder until sufficient brake cylinder pressure is producedto deflect the pressure responsive member 2ll to close the inshot valveand the brake cylinder maintaining valve.

It is to be understood that the foregoing description of operationassumes that the rate of reduction of brake pipe pressure isinsufficient to deflect the pressure responsive member 40 of theemergency portion, the quick action chamber pressure flowing back intothe brake pipe via the choke 63 and the check valve 57 causing thepressure differential across the pressure responsive member to not besufficient to deflect the member 44 against the spring 46.

Release after a service application as indicated above, is effected bythe drivers brake valve producing a recovery of brake pipe pressuretowards the normal steady value. if therefore the brake pipe pressure isso increased, a pressure differential is produced across the pressureresponsive member 1 of the service portion of the apparatus to cause adownward force which is resisted by the upward force of brake pipepressure in the bulb capacity 14 on the quick service valve member 10and the underside of the stem 2. As soon as this force is overcome, thepressure responsive member moves downwards and the sleeve member 12 ofthe quick service valve arrangement descends until it reaches its loweststop by which time the valve closure member 10 is in engagement with theslidable sleeve 11 so that the quick service inlet valve is closedbefore the quick service exhaust valve is opened. This ensures thatduring the releasing operation, there is no communication in the quickservice valve arrangement between the brake pipe, the quick service bulbcapacity and atmosphere. Further increase in the pressure differenceacross the diaphragm is thus effected by exhausting of the bulb pressureunder the stem 2 and such increase in pressure differential causes rapiddownward movement of the pressure responsive member to open the brakecylinder exhaust valve 5, the auxiliary reservoir charging valve 6, andthe emergency reservoir charging valve 7. Releasing brake cylinder airflows to atmosphere via the airway A6, the valve 5 and the exhaustpassage R1. The exhaust pressure in the passage R1 operates beneath thepressure responsive member 17 of the accelerated release valve 18 andthe member 17 therefore temporarily moves upwards to provide acommunication between the emergency reservoir whose pressure is abovethe valve 18 and the brake pipe. By virtue of the choke 16, the pressureafter a short interval equalizes across the pressure responsive member17 and the valve 18 recloses. Operation of the accelerated release valve18 for this brief interval assists the rapid propogation of a brakerelease along a train by the flow of emergency reservoir air into thebrake pipe augmenting increase of brake pipe pressure from the driversbrake valve.

It will be further noted that since the pressure in the quick servicebulb capacity 14 is now vented via the quick service vent valve 10, thebulb pressure beneath the piston of the slidable sleeve 1 1 falls andthe piston is held against the housed spring in the position shown inthe drawing. The release position is thus regained in which the pressureresponsive member 1 and the components beneath it are urged downwardsagainst this housed spring by the resultant of brake pipe pressure inthe chamber (b) over the area of the stem 2 against atmospheric pressurein the quick service bulb 14.

The operation has been described so far on the assumption that the ratesof change of brake pipe pressure have been only sufficient to causeoperation of the service portion of the apparatus but if the brake pipepressure is rapidly dropped as for an emergency brake application, thereduction of brake pipe pressure effective in the chamber (p) beneaththe pressure responsive member 40 of the emergency portion of theapparatus is more rapid than can be compensated for by flow of air viathe choke 63 and the check valve 57. The upward force of brake pipepressure in the passage B1 and the force of the spring 46 beneath thevent valve 44 is therefore overcome and the pressure responsive membermoves downwards to open the vent valve 44. The brake pipe pressure istherefore rapidly vented to atmosphere via the passage B1 and the openvalve 44.

The pressure responsive member and stem 43 continue to move downwards tofully open the high pressure valve 50 to connect the emergency reservoirvia the passage E2 to the emergency inshot valve 53, the open conditionof which permits this emergency reservoir air to be applied directly tothe brake cylinder at BC.

It will be appreciated moreover that the action of brake pipe pressurealso enables the service portion described above, to operate in themanner of a service application and supply air from the auxiliaryreservoir to the brake cylinder. Under an emergency applicationtherefore the auxiliary reservoir air is supplemented by emergencyreservoir air to effect a rapid application. Also, the operation of theemergency portion can be arranged to provide a 20 percent (say) increasein the pressure in the brake cylinder as compared with that which isproduced for a given reduction of brake pipe pressure purely by theservice portion.

As mentioned previously, the inshot valve 53 is arranged by virtue ofthe spring pressure of the spring 54 and the dimensioning of thepressure responsive member 55 to remain open until brake cylinderpressure attains approximately 12 p.s.i. The build up of air in thebrake cylinder for an emergency application is therefore very rapid tobegin with following sufficiently rapid drop of brake pipe pressureuntil the point at which the valve 53 closes. After this time a build upof brake pipe pressure is governed by the choke 56.

Downward movement of the pressure responsive member 40 of the emergencyportion causes the valve ball 58 to lift off the needle 60 so that thechoke 63 is no longer bypassed via the valve 58 and the flow of airbetween the chambers (q) and (p) on either side of the pressureresponsive member can only pass via the chokes 62 and 63 in series withthe check valve 57. This enables a clean and rapid function such thatthe vent valve 44 is held open for a prolonged time until the quickaction chamber pressure falls to a lower value at which the spring 46can reclose the vent valve 44 and also permit the high pressure valve 50to close interrupting the communication between brake cylinder andemergency reservoir.

The sequence of events during a brake release operation following arapid reduction of brake pipe pressure which has given rise to operationof the emergency portion as described above may now be considered. Whenthe brake pipe pressure is recharged, it is effective in the chamber (p)to permit upward movement of the pressure responsive member 40 againstthe housed spring 65 shown above it. This permits the emergencyaccelerated release valve 47 to lift off its seat provided on thesliding member 49 and thereby provides a path from on the one hand thebrake cylinder and on the other hand the auxiliary reservoir via theopen brake cylinder inlet valve 4 of the service portion to flow to thebrake pipe via passages A7 and A8. An accelerated build up of brake pipepressure is thereby effected and since the auxiliary reservoir pressureis thereby also reduced the service portion operates to a releasecondition at an earlier instant in time since brake pipe pressure isrequired to recover to a lower pressure to effect movement of thepressure responsive member 1. The emergency accelerated release valve 47in conjunction with its spring 48 operates as a check valve such that itrecloses when the auxiliary reservoir and brake cylinder pressures haveattained values within approximately p.s.i. of the brake pipe pressure.Subsequently, the pressures in the chambers (p) and (q) move towards oneanother by virtue of the choke 64 and check valve 59 and the member 40returns to a position as shown in the drawing. It will be appreciatedthat a substantial reduction of auxiliary reservoir pressure isexperienced during an emergency operation and recharging of theauxiliary reservoir is effected as described previously via the serviceportion auxiliary reservoir charging valve and the retarded rechargevalve 30 affords a controlled recharge by enabling a fixed pressuredifferential to be produced across the choke 33 as described previously.Similarly, recharging of the emergency reservoir is effected asdescribed before via the valve 7.

In order that a typical manner of operation may readily be envisaged onthe basis of the foregoing description, it may for example be visualizedthat the normal running brake pipe pressure may be 70 p.s.i. and thepressure responsive member of the service portion moves towardsapplication of brakes when the brake pipe pressures falls below 0.75p.s.i. of the auxiliary reservoir pressure. The service portionsubsequently laps off to a stable lap position with brake cylinder valveclosed when the brake pipe is at approximately auxiliary reservoirpressure. 7

The volumes may typically be so designed moreover that under serviceapplication conditions, a drop of brake pipe pressure of p.s.i. willgive a full service brake application of 50 p.s.i. brake cylinderpressure. Intermediate higher brake pipe pressures provide intermediatelower brake cylinder pressures.

Brake release under service application conditions is effected by a riseof brake pipe pressure of 1.5 p.s.i. above the auxiliary reservoirpressure, this being sufficient to cause downward movement of thepressure responsive member 1 from the lap position towards a position toopen the brake cylinder exhaust valve.

If the rate of fall of brake pipe pressure on application conditions issufficient and fast enough, the emergency portion operates with theservice portion to enhance the brake cylinder pressure to produce anemergency brake application. Typically the choke 63 and the check valve57 of the emergency portion are so dimensioned that a drop of brake pipepressure from 70 to 50 p.s.i. in 2 seconds will cause an emergencyoperation by opening vent valve 44 whereas a drop of from 70 to 50p.s.i. in three seconds will cause only a service application.Additionally, small reductions of brake pipe pressure, of say 8 p.s.i.or less will not of themselves alone, however fast, effect the emergencyportion.

After an emergency application, a reset time for the vent valve isarranged by choice of chokes 62 and 63,

to be of the order of one minute. Additionally, recharge of theemergency portion is arranged to be fully effected from 0 to p.s.i. viachoke 64 in approximately 1 minute.

Having thus described my invention what I claim is:

l. Fluid operable brake control apparatus for controlling, in responseto brake pipe pressure, the supply of fluid under pressure into and outof a brake cylinder, the apparatus including a first chamber at brakepipe pressure and a second chamber at reference pressure, a uid pressureresponsive member separating the first and second chambers, choke meansbetween said chambers, a brake cylinder valve and a vent valve, thebrake cylinder valve being connected between a fluid pressure reservoirand a brake cylinder port, the vent valve being connected between abrake pipe port and an exhaust port, means linking both said valves tothe pressure responsive member so as to be opened by movement of thepressure responsive member when a fall of brake pipe pressure inrelation to the reference pressure is sufficiently rapid as to not becompensated for by fluid flow in the choke means, and an acceleratedrelease valve connected between the brake cylinder port and the brakepipe and so mechanically coupled to the pressure responsive member as tobe opened when a recovery of brake pipe pressure in the first chamberbeyond a reduced reference pressure in the second chamber takes placeafter reclosure of the brake cylinder valve and the vent valve.

2. Fluid operable brake control valve apparatus as claimed in claim 1,the vent valve, the brake cylinder valve and the accelerated releasevalve all being disposed in an in-line arrangement.

3. Fluid operable brake control valve apparatus as claimed in claim 2wherein the accelerated release valve comprises a closure member and aseat which are movable as one in the closed position thereof, and thebrake cylinder valve being operable by the pressure responsive membervia an actuating rod and the movable accelerated release valve.

4. Fluid operable brake control valve apparatus as claimed in claim 3,further comprising resilient means for resiliently urging theaccelerated release valve towards the closed position in the releaseposition of the apparatus in order that it operates as a check valveduring brake release operation and closes at a predetermined value ofpressure difference between the brake pipe and the brake cylinder 5.Fluid operable brake control valve apparatus as claimed in claim 1arranged and connected to operate as an emergency valve in combinationwith a service application controlling triple valve which is responsiveto less than said predetermined change of brake pipe pressure.

1. Fluid operable brake control apparatus for controlling, in responseto brake pipe pressure, the supply of fluid under pressure into and outof a brake cylinder, the apparatus including a first chamber at brakepipe pressure and a second chambEr at reference pressure, a fluidpressure responsive member separating the first and second chambers,choke means between said chambers, a brake cylinder valve and a ventvalve, the brake cylinder valve being connected between a fluid pressurereservoir and a brake cylinder port, the vent valve being connectedbetween a brake pipe port and an exhaust port, means linking both saidvalves to the pressure responsive member so as to be opened by movementof the pressure responsive member when a fall of brake pipe pressure inrelation to the reference pressure is sufficiently rapid as to not becompensated for by fluid flow in the choke means, and an acceleratedrelease valve connected between the brake cylinder port and the brakepipe and so mechanically coupled to the pressure responsive member as tobe opened when a recovery of brake pipe pressure in the first chamberbeyond a reduced reference pressure in the second chamber takes placeafter reclosure of the brake cylinder valve and the vent valve.
 2. Fluidoperable brake control valve apparatus as claimed in claim 1, the ventvalve, the brake cylinder valve and the accelerated release valve allbeing disposed in an in-line arrangement.
 3. Fluid operable brakecontrol valve apparatus as claimed in claim 2 wherein the acceleratedrelease valve comprises a closure member and a seat which are movable asone in the closed position thereof, and the brake cylinder valve beingoperable by the pressure responsive member via an actuating rod and themovable accelerated release valve.
 4. Fluid operable brake control valveapparatus as claimed in claim 3, further comprising resilient means forresiliently urging the accelerated release valve towards the closedposition in the release position of the apparatus in order that itoperates as a check valve during brake release operation and closes at apredetermined value of pressure difference between the brake pipe andthe brake cylinder
 5. Fluid operable brake control valve apparatus asclaimed in claim 1 arranged and connected to operate as an emergencyvalve in combination with a service application controlling triple valvewhich is responsive to less than said predetermined change of brake pipepressure.